Well, here's part of the way to do it, release a CHEAP Dual-SIM all-touch phone and sell it in developing countries where pay-as-you-go and pre-paid cards are predominant.
Here's Nokia first all-touch Dual-Sim S40 device, the leaked photos originated from Taiwan, China.
You can see the 2nd SIM slot in the second photo.
From the photos we can conclude that
It's a 3.2inch screen,
it looks kinda bulky but the curved back makes it easier to grip,
it has a microSD slot,
make call and end call physical buttons.
3.5mm audio jack,
normal Nokia a/c jack
It's almost certain this will run on Symbian series40 OS.